import java.util.Stack;

public class MinStack {
    private Stack<Integer> stack;
    private Stack<Integer> minStack;

    public MinStack(){
        stack = new Stack<>();
        minStack = new Stack<>();
    }
    public void push(int val){
        stack.push(val);
        if (minStack.empty()){
            minStack.push(val);
        }else {
            if (val <= minStack.peek()){
                minStack.push(val);
            }
        }
    }
    public void pop(){
        if (!stack.empty()){
           int ret =  stack.pop();
            if (minStack.peek() == ret){
                minStack.pop();
            }
        }
    }
    public int top(){
        if (stack.empty()){
            return -1;
        }else {
            return stack.peek();
        }
    }
    public int getMin(){
        if (minStack.empty()){
            return -1;
        }
        return minStack.peek();
    }
}
